Reducing moisture on and in harvested crops prior to their storage.
The harvesting and storage of crops, and especially the storage of crops for a substantial period of time, is heavily affected by moisture of the atmosphere and of the moisture within the collected crop itself. Crops are harvested while under widely varying atmospheric conditions. Heavy dew, recent rain, and drought are examples of circumstances faced by harvesters of field crops due to atmospheric conditions. In addition, the moisture content in the particles of crop, for example inside the outer membrane of a grain of corn, count as part of the moisture of concern. The subsequent storage of a crop in structures such as elevators and silos is highly sensitive to moisture content from any source, and these structures can tolerate moisture levels only below certain threshold values relating to integrity of the crop and of the structure itself.
For example, when corn is to be stored after harvest, it is common practice for an elevator to refuse to store grain with a total moisture content greater than 14%. Of course a crop which is brought to the elevator might have a moisture content higher or lower than that, but if it is higher, the elevator proprietor will either refuse to store it, or will levy a surcharge to pay for him to reduce the moisture content to an acceptable level. This is a substantial surcharge which the farmer will much prefer to avoid. Furthermore, the reduction of moisture is generally done with heated air, whose heat is derived from a propane flame. The cost for this process is a function of how much moisture needs to be removed, and of course on the current unit price of propane. In whatever event, the requirement for heat involves an uncertain expense that cannot be predicted, and also involves release of carbon compounds into the atmosphere that is subject to regulation which is certain to become even more stringent.
It should be remembered that it is not the object of the invention to xe2x80x9cdryxe2x80x9d the crop in the sense of desiccation. Crops with moisture are regularly and routinely stored. The function of this invention is to bring down the moisture level to or toward an acceptable level by affordable means.
Increased fuel cost and environmental adversity are not the only objectionable complications of moisture content in the crop. The unavoidable additional physical handling of the crop required by the moisture-removing process can lead to degradation of the physical characteristics of the crop itself, such as by causing bruising, scratching and fragmentation of the product. This invention minimizes those risks.
It is an object of this invention to utilize the combination of two moisture-reducing techniques which, when used together result in a surprising reduction of moisture compared to the comparable use of one of them alone, or each separately.
In addition, and as an optional objective, use can be made in the field, on the harvester itself, of an inherent source of heat which in current practice is wasted to the atmosphere, or at best a very small amount is directed to heating the operator""s cabin. By heat-treating the crop with waste heat from the engine while the crop is being harvested, the requirement for a later moisture reduction can be significantly reduced, and sometimes eliminated entirely. This also can reduce the handling of the crop.
This invention thereby provides a means to improve a harvested crop not only just before storage, but if desired also while it is being harvested, so that with less handling and less fuel cost, the crop can be made ready for storage.
In this specification, the harvesting and treatment of corn is provided as an example for illustration purposes. The invention is applicable also to any other crop that can be stored in elevators or silos. Examples of other crops with which this invention is useful are soybeans, wheat and rye.
According to this invention, the harvested crop, for example shelled corn, is heated to reduce its moisture should existing moisture of the crop as harvested in the field exceed levels acceptable for storage. The heat can be provided in two forms: first, a heated airstream flowing over and through the crop, and second, microwave energies injected into the crop at frequencies which are utilized to vaporize water. Such frequencies are commonly utilized in microwave ovens.
The heating effect of these frequencies resides in the vaporization of water in the product to be heated. While these frequencies are effective for removing surface moisture, their greater value in this invention is for vaporizing water inside the particles of product themselves. This energy can be applied independently of a heated airstream.
According to a preferred but optional feature of the apparatus and method, the apparatus is mounted to or towed along with a harvester while it is harvesting the crop. Exhaust heat from the harvester engine is utilized to heat an airstream which flows over, into, and through the crop as one step in drying the crop. Conventionally this engine heat is wasted to the atmosphere by cooling the radiator or in the exhaust gases from the engine. In this embodiment, engine heat developed in excess of motive requirements is not wasted. Rather it is used beneficially. If desired, an auxiliary source of heat, even a burner can be used along with it, or separately, or a somewhat larger engine than is needed for propulsion and operation of the harvesting machinery may be installed.
Energy in the two forms is preferably applied simultaneously, so the flowing heated airstream can assist in removing vaporized water which has passed from the inside of the particle to the outside of it, and can be carried away in the airstream, along with such water as existed on the surface of the crop when the crop was harvested.
Advantages are provided by exerting the microwave energy at least some of the time while engine heat is also being applied. It is best practice to start both of them as soon as possible, preferably in the field. Preheating the crop with hot gas before treating it with microwave energy also provides advantages.
As a consequence of any of the available arrangements, the farmer himself is enabled to reduce the moisture in the crop with least damage to the crop, and without any surcharge (or at least only with a reduced surcharge) to be paid at the elevator. The potential savings are in fact quite large, and go straight to the farmer""s bottom line. Again it is emphasized that the objective is to reduce moisture to an acceptable level, rather than to xe2x80x9cdryxe2x80x9d the crop.
It is an additional preferred but optional feature of the invention to reduce physical wear on the crop as it is being handled, by utilizing a fluidics system for moving the harvested crop instead of using the mechanical rotary-type augers or buckets that are conventionally used to propel the crop in a harvester system beyond the thresher head.
The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings, in which: